近日，德国哥廷根大学Stefan Mathias团队研究了石墨烯中Floquet态的观测。2025年5月6日，《自然—物理学》杂志发表了这一成果。
Floquet工程——通过时间周期性扰动对物质进行相干修整——是一种实现和控制材料中不平衡的涌现相的机制。然而，它对金属量子材料和石墨烯等半金属的适用性是一个悬而未决的问题。石墨烯中光诱导反常霍尔效应的报告仍存在争议，时间分辨光电发射实验表明，Floquet效应可能无法在石墨烯和其他退相干时间相对较短的半金属中实现。
研究组通过电子结构测量提供了石墨烯中Floquet效应的直接光谱证据。通过测量Floquet边带、Volkov边带及其量子路径干涉对石墨烯光电发射光谱的贡献来观察光物质修饰的狄拉克带。该结果表明，石墨烯中的Floquet工程是可能的，即使超快退相干过程发生在几十飞秒的时间尺度上。该方法提供了一种在金属和半金属系统中实验实现Floquet工程策略的方法，以及具有潜在非平凡拓扑性质的光诱导态的相干稳定方法。
附：英文原文
Title: Observation of Floquet states in graphene
Author: Merboldt, Marco, Schler, Michael, Schmitt, David, Bange, Jan Philipp, Bennecke, Wiebke, Gadge, Karun, Pierz, Klaus, Schumacher, Hans Werner, Momeni, Davood, Steil, Daniel, Manmana, Salvatore R., Sentef, Michael A., Reutzel, Marcel, Mathias, Stefan
Issue&Volume: 2025-05-06
Abstract: Floquet engineering—the coherent dressing of matter via time-periodic perturbations—is a mechanism to realize and control emergent phases in materials out of equilibrium. However, its applicability to metallic quantum materials and semimetals such as graphene is an open question. The report of light-induced anomalous Hall effect in graphene remains debated, and a time-resolved photoemission experiment has suggested that Floquet effects might not be realizable in graphene and other semimetals with relatively short decoherence times. Here we provide direct spectroscopic evidence of Floquet effects in graphene through electronic structure measurements. We observe light–matter-dressed Dirac bands by measuring the contribution of Floquet sidebands, Volkov sidebands and their quantum path interference to graphene’s photoemission spectrum. Our results demonstrate that Floquet engineering in graphene is possible, even though ultrafast decoherence processes occur on the timescale of a few tens of femtoseconds. Our approach offers a way to experimentally realize Floquet engineering strategies in metallic and semimetallic systems and for the coherent stabilization of light-induced states with potentially non-trivial topological properties.
DOI: 10.1038/s41567-025-02889-7
Source: https://www.nature.com/articles/s41567-025-02889-7